102 A TOUR AMONG THE ISLANDS 



The shore is composed of broken rocks, and the forest 

 comes to the water, but there is very little undergrowth 

 of bushes, so that we were able to walk about freely. 



Glossina was absent : the other arthropod life was of 

 great interest. The first thing noticed was the abundance 

 of very large, long-legged black and yellow spiders 

 (Nephila), which spin webs several feet in diameter. 

 These great webs formed sheets, often in planes one behind 

 another when the branches offered suitable support, 

 so closely placed that the spiders on the central sheets 

 could hardly get any insects on their webs, and looked 

 starved. Sanga, therefore, was known as a " spider 

 island," and others will be described later. The next 

 feature noted was the unusual abundance of predaceous 

 Mantidae, and this was associated with absence of insecti- 

 vorous birds ; a very interesting example of the " balance 

 of nature." 



At the time of this visit, and we remained on the island 

 several hours searching it thoroughly, I neither saw nor 

 heard a single flycatcher, bee-eater, coucal, or any of 

 the common small warblers ; parrots and weavers were 

 the only birds noted in the forest. At a second visit, 

 however, one " Kunguvu " flycatcher was noted, and the 

 call of a common cuckoo was heard. Perhaps correlated 

 with this absence of insectivorous birds was the fact, 

 which Fiske and I noted independently, that the butter- 

 flies, especially the mimetic Euralia and Aterica galene 

 which I have always found very difficult to catch on account 

 of their shyness, were here much less shy and easier to 

 catch. Fiske thought that it was on account of the 

 multitude of spiders' webs, which had resulted in the 

 butterflies flying more slowly and cautiously to avoid 

 them ; but I noticed that when on the ground the mimics 

 were more easily approached than is usually the case. 



The numbers of butterflies found on Sanga are given in 

 the table (p. 125) ; the most noteworthy feature was unusual 



